UPDATE: Our GitHub Actions now run mypy --ignore-missing-imports excluding those directories that fail that test.

• https://github.com/TheAlgorithms/Python/blob/master/mypy.ini#L5

Currently, we are not running mypy in our regular CI tests as there are a lot of errors in the entire codebase, which needs to be fixed. This won't be a one-person job, so we are asking for help from you. I cannot paste the entire message in here as there are around 600 of them, so here's just a gist of it:

$ mypy --ignore-missing-imports .
strings/word_occurrence.py:17: error: Need type annotation for 'occurrence'
strings/min_cost_string_conversion.py:36: error: No overload variant of "__setitem__" of "list" matches argument types "int", "str"
strings/min_cost_string_conversion.py:36: note: Possible overload variants:
strings/min_cost_string_conversion.py:36: note:     def __setitem__(self, int, int) -> None
strings/min_cost_string_conversion.py:36: note:     def __setitem__(self, slice, Iterable[int]) -> None
strings/min_cost_string_conversion.py:40: error: No overload variant of "__setitem__" of "list" matches argument types "int", "str"
strings/min_cost_string_conversion.py:40: note: Possible overload variants:
strings/min_cost_string_conversion.py:40: note:     def __setitem__(self, int, int) -> None
strings/min_cost_string_conversion.py:40: note:     def __setitem__(self, slice, Iterable[int]) -> None
...
backtracking/n_queens_math.py:109: error: List comprehension has incompatible type List[str]; expected List[int]
backtracking/n_queens_math.py:110: error: Argument 1 to "append" of "list" has incompatible type "List[int]"; expected "List[str]"
backtracking/n_queens_math.py:149: error: Need type annotation for 'boards' (hint: "boards: List[<type>] = ...")
backtracking/minimax.py:15: error: "list" is not subscriptable, use "typing.List" instead
backtracking/knight_tour.py:6: error: "tuple" is not subscriptable, use "typing.Tuple" instead
backtracking/knight_tour.py:6: error: "list" is not subscriptable, use "typing.List" instead
...

Guidelines to follow:

• Please make sure you read the Contributing Guidelines first.
• Please submit a fix for a maximum of 3 files at a time (1 file is also acceptable).
• As we are not running mypy in our CI tests, the user who is submitting a pull request should run it on their local machine and ensure there are no errors in their submission.
• Please ensure your pull request title contains the word mypy in it. If possible use this template for your pull request title:

[mypy] Fix type annotations for <filenames>

Which errors to fix?

Please follow the below steps to produce all the errors in this library:

• Fork this repository if you haven't already.
• Clone the forked repository on your local machine using the command:

git clone --depth 1 https://github.com/TheAlgorithms/Python.git

Then you need to install all the necessary requirements:

cd python/
python -m pip install --upgrade pip
python -m pip install -r requirements.txt
python -m pip install mypy

Then run either of the two commands:

• mypy --ignore-missing-imports . -> To produce all the error messages for the entire codebase.
• mypy --ignore-missing-imports <filepath1> <filepath2> ... -> To produce error messages for the mentioned file.

How to fix the errors?

• Make a separate branch for your fix with the command:

git checkout -b mypy-fix

• Make changes to the selected files.
• Push it to your forked copy and open a pull request with the appropriate title as mentioned above.

Focus on one directory at a time:

.
├── [x] arithmetic_analysis
├── [x] backtracking
├── [x] bit_manipulation
├── [x] blockchain
├── [x] boolean_algebra
├── [x] cellular_automata
├── [x] ciphers
├── [x] compression
├── [x] computer_vision
├── [x] conversions
├── [ ] data_structures
├── [x] digital_image_processing
├── [x] divide_and_conquer
├── [ ] dynamic_programming
├── [x] electronics
├── [x] file_transfer
├── [x] fractals
├── [x] fuzzy_logic
├── [x] genetic_algorithm
├── [x] geodesy
├── [x] graphics
├── [ ] graphs
├── [x] hashes
├── [x] knapsack
├── [x] linear_algebra
├── [x] machine_learning
├── [ ] maths
├── [ ] matrix
├── [x] networking_flow
├── [x] neural_network
├── [ ] other
├── [ ] project_euler
├── [x] quantum
├── [x] scheduling
├── [x] scripts
├── [ ] searches
├── [x] sorts
├── [ ] strings
└── [x] web_programming

Pre-requisites:

• You should be familiar with mypy: https://mypy.readthedocs.io
• You should be familiar with Python type hints: https://docs.python.org/3/library/typing.html